The vibration - rotation motions of water molecules in aqueous ZnCl solution

An analysis of the frequency distribution function of hydration water molecules at various concentration in ZnCl solution extracted from results of the inelastic slow neutron scattering experiments is presented. The frequency spectrum corresponding to the translation modes (bending of hydrogen bonds at energy transfer, ε ∼ 6 - 7 meV, stretching of hydrogen bonds at energy transfer, e ∼ 12 - 20 meV) as well as the frequency spectrum of the proton libration mode are derived from experiments. As the concentration is increased up to the saturation limit (12.6 M) more than two translation modes are observed. Additional information related to the dynamics of hydration water are obtained from the translation velocity autocorrelation function for pure water and for hydration water. (authors)